Bell and Howell 785 User Manual

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GENERAL
INFORMATION
This manual
covers the following
Bell
& Howell
tape recorders:
Models
?85,
?85C,
?85L,
?85ST-4,
?85X,
and ?85-4TS.
The differences
between these
models
are as follows:
Model ?85-4TS
will record
four
tracks
monaural
orplay
back twoor
four
track
pre-recorded
stereo tapel
Model?8bis
designed
for
ll?
volt, 60
cygfe
AC
operationl
Model ?85-C
is
designed for ll?
volts,
b0 to
60
cycle AC
operationl
Model 785-L
is
equipped
wi.th
a 3-wire
power
cable and
grounding
type
plugj
Uodel
?85-X
is
designed
for
ll0
or 220 volts,
b0
or 60 cycle
AC.
All
models
wilt a'bcept
reels
up
to
? inches
in
diameter.
Each mode
of operation is
con-
trolled
by a
pushbutton.
The
tape
speeds
are 3
3/
4
-ips.and
7
L/ 2 tps.
Using
a
1200 ft. reel
of tape
on four tracks,
the
playing
or recording
time at
3 3/4 ips
is
four
hours; at 7
L/ 2 ips is
two
hburs.
Connect the
recorder
to the
power
source
specified for the
model
being
used.
Supplied
By:
Bell
&
Howell Co.
7125
North Kimball
Avenue
Chicago
45,
lllinois
HOWARD
W.
SAIUIS
&
The lieting
of
any
available replacement part
herein does
not
constitute
in
any case
a recommendation,
warranty or
guarantyby
Howard
W.
Sams
& Co., Inc.,
as to the
quality
and
guitability
of such
replacement part.
The numbers
of
these parts
have
been
compiled from
information
furnished
to
Howard
W. Sams
&
Co.
,
Inc.
,
by
the
manufacturers
of
cQ4?8
G
CD., I t
(C.
tndianapolls
€i,
lndiana
the
particular
type
of
replacement
part
listed.
Repro-
duction or use,
without express
permission,
of editorial
or
pictorial
content,
in
any manner,
is
prohibited.
No
patent
liability
is
assumed.with respect to the use
ol the informa-
tion
contained
herein.
@
ISOZ Howard
W.
Sams
& Co.
,
Inc.
,
q
l-r
-l
cJr
clt
t\9
-l
€
E
ITI
-
Indianapolis
6, Indiana.
DATE
I
-
62
Printed in
U.S.
of
America
sET 562 FOTDER 1

Bell and Howell 785 Specifications

General

Brand	Bell and Howell
Model	785
Category	Voice Recorder
Language	English

Summary

General Information

Bell & Howell Tape Recorder Model Overview

Details on models 785, 785C, 785L, 785ST-4, 785X, 785-4TS and their differences.

Tape Speed and Recording Time Specifications

Information on reel size, operating controls, tape speeds, and recording times.

Controls and Operation

Control Panel Functions Explained

Explanation of all controls including volume, tone, monitor, buttons, and selectors.

Key Operating Procedures

Steps for threading tape, recording, playback, erasing, and pausing.

Tape Playback Procedures

Playing Dual-Track Tapes

Instructions for playing two-track tapes on the recorder.

Playing 4-Track Tapes

Guide for playing four-track tapes, including switching sides.

Stereophonic Playback Guide

Steps for connecting and playing stereo recordings.

Maintenance and Advanced Features

Recorder Disassembly and Component Removal

Detailed steps for disassembling the recorder, transport, and amplifier.

Operational Adjustments and Features

Guides on pressure roller, take-up tension, public address, and rewind/fast-forward.

Component Adjustments and Cleaning

Play-Record Head Adjustment Procedure

Procedure for adjusting the play-record head for optimal performance.

Cleaning and Lubrication Instructions

How to clean key components and information on lubrication.

Technical Schematics and Component Data

Electronic Circuit Schematic Diagrams

Detailed circuit diagrams for the tape recorder's electronic sections.

Component Resistance and Voltage Readings

Tables showing resistance readings and voltage measurements for various components.

Component Layout Diagrams

Amplifier Chassis Top View Layout

Top view of the amplifier chassis showing component placement.

Printed Circuit Board Top View Layout

Top view of the printed circuit board with component identification.

Printed Board Component Identification

12AX7 and 6S4A Tube Component Layout

Identification of components on the printed board around 12AX7 and 6S4A tubes.

6CM6 and 12AT7 Tube Component Layout

Identification of components on the printed board around 6CM6 and 12AT7 tubes.

Electrical Parts List and Descriptions

Tube and Resistor Specifications and Replacements

List of tubes and resistors with their types, ratings, and replacement data.

Capacitor, Coil, and Transformer Data

Details on capacitors, RF/IF coils, and power/audio transformers.

Speaker, Miscellaneous, and Wiring Data

Information on speakers, miscellaneous parts, and wiring data.

Troubleshooting Guide

Common Operational Issues and Causes

Lists common problems like noise, binding controls, and drive issues with their causes.

Solutions for Tape Transport Problems

Remedies for take-up reel, supply reel, and general drive system malfunctions.

Addressing Sound Quality and Stopping Issues

Solutions for pitch distortion, stopping mechanism failures, and wow/flutter.

Mechanical Parts List

Fasteners and Small Mechanical Parts List

Listing of screws, washers, rings, springs, and other small mechanical components.

Major Mechanical Assemblies and Components List

Details on major parts like spindles, heads, rollers, motors, and levers.